Despite years of research into the development of new methods of treatment, cancers of the lymphatic system, or lymphomas, remain quite common. For example, more than 60,000 people in the United States are diagnosed with lymphoma each year, including more than 55,000 cases of non-Hodgkin's Lymphoma (NHL), and these numbers are constantly increasing. In addition, the prognosis for those affected by these diseases is often poor, as the survival rates for lymphoma patients remain low. Clearly, new methods for treating these diseases are needed.
While traditional treatments for lymphoma typically depend on the type of lymphoma as well as the medical history of the patient, first-line treatment for many lymphomas typically includes chemotherapy. Such chemotherapy will often entail the administration of a “cocktail” of compounds, e.g., the formulation CHOP, which includes cyclophosphamide, doxorubicin, vincristine, and prednisone. In addition, certain first-line cancer treatments also include other forms of cancer therapy, such as radiation therapy.
In many cases, patients respond initially to such first-line treatments, but subsequently suffer a relapse, i.e., a tumor reappears or resumes growing. Following one such relapse, patients are often treated with further chemotherapy, e.g., with CHOP or with other formulations, or, in some cases, the patients are treated with other procedures such as bone marrow transplantation. Again, in many cases, patients initially respond to such additional treatments, but subsequently suffer another relapse. In general, the more relapses a patient suffers, the less agreement there is in the art concerning optimal subsequent treatment. In other cases, a patient fails to respond at all to a treatment, even initially, and is thus said to have a refractory cancer. In such cases as well, little agreement exists in the art regarding optimal subsequent treatment.
Alkaloids isolated from the periwinkle plant (Vinca rosea), called “vinca alkaloids,” have proven effective for first line treatments of many types of lymphomas, leukemia, and other cancers. One such vinca alkaloid, vincristine, is included in the common chemotherapeutic formulation CHOP. Vincristine, which depolymerizes microtubules and thereby inhibits cell proliferation, is administered in its free form in CHOP. Liposome-encapsulated vincristine has been reported (see, e.g., U.S. Pat. No. 5,741,516, or U.S. Pat. No. 5,714,163). In particular, these patents discuss the use of vincristine encapsulated in phosphatidylcholine, distearoylphosphatidylcholine, or sphingomyelin, in addition to cholesterol. Successful clinical applications of this technology, however, have never been achieved. Indeed, major theoretical and practical uncertainties remain, including uncertainties regarding biodistribution, toxicity, and efficacy.
Lipid-encapsulated drug formulations may provide advantages over traditional drug-delivery methods. For example, some lipid-based formulations provide longer half-lives in vivo, superior tissue targeting, and decreased toxicity. Numerous methods have been described for the formulation of lipid-based drug delivery vehicles (see, e.g., U.S. Pat. No. 5,741,516). No studies, however, have demonstrated that such liposome-encapsulated vinca alkaloid formulations offer any advantages over previous treatments, or have efficacy in the in vivo treatment of cancer in a patient. As such, there remains a need in the art for new methods for treating these diseases. Quite surprisingly, the present invention provides such methods.